


Siding Springs

by alessandriana



Category: The Martian (2015), The Martian - All Media Types, The Martian - Andy Weir
Genre: Ares III has terrible luck, Case Fic, Gen
Language: English
Status: Completed
Published: 2017-12-31
Updated: 2017-12-31
Packaged: 2019-02-16 12:09:41
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 6,600
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13053708
Author URL: https://archiveofourown.org/users/alessandriana/pseuds/alessandriana
Summary: "Oh, hey, Vogel, you've got a telemetry update, and Commander, there's a space weather advisory for the crew.""What does it say?" Lewis asked, coming to stand behind Johanssen."Hmm... we're going to be passing through the tail end of a comet debris field starting this afternoon, so there will be a slightly increased chance of micrometeoroid impacts."Slightly increased? Yeah, it’s Ares III. Our luck is just not that good.





	Siding Springs

**Author's Note:**

  * For [laura47](https://archiveofourown.org/users/laura47/gifts).



[Mission Day 748]

I would like to state for the record (literally, since these logs are official government documents) that I am really fucking sick and tired of having broken ribs. It's been 61 days since I got launched off the surface of Mars in a MAV-turned-convertible, and they still haven't healed all the way.

Beck has a lot of theories-- low-g causes bone loss under normal circumstances, and when you add in the effects of chronic malnutrition, I'm basically the poster boy for worst case scenario injury healing-- but I honestly don't care. I am really fucking tired of feeling like someone stuck a fork in my side every time I take a deep breath.

Anyways.

It's day 6 of zero-g fern growth experiment v2.0 (Beck ran 1.0 on the first trip back from Mars, but-- well, I'm gonna be honest here, Beck is not a botanist, and NASA thought the results indicated something might have gone wrong with the experiment, so they're having me do it again), and I am otherwise on light duties, so my schedule for the day consists of 1) eating breakfast, 2) reading mail from home, 3) measuring plant leaves, and 4) maybe watching a movie.

I really enjoy this whole 'not living on the precipice of constant death' thing.

 

***

 

_Comet C/2013 A1 (Siding Springs) was first discovered on its way through the solar system in early 2013 by the Siding Springs Observatory in Australia. Born in the Oort Cloud some 4.6 billion years ago, it was ejected some time later and eventually worked its way into a million-year orbit around the sun. It passed perihelion-- the closest point in its orbit to the sun-- in 2014. Being a relatively small comet, it was only visible on Earth to those with telescopes._

_There would have been little of note about Comet Siding Springs if it hadn't been for its path, which brought it within 140,000 km of Mars in October of 2014-- one third of the distance between the Moon and Earth. This glancing blow caused an intense meteor shower on Mars' surface and generated wild but temporary perturbations of both Mars' magnetic field as well as a number of academic conferences on Earth._

_As it left Mars, Comet Siding Springs shed a trail of debris that stretched out behind it._

 

***

 

Watney slid into the chair next to Johanssen, food pack in hand. "How's the data dump coming?" he asked as he peeled back the lid. Lewis leaned against the wall, arms crossed. Even now that Watney was safe and back on the ship, she never missed a single transmission from Earth.

Johanssen said, "Almost there... okay, done. Personal emails have been forwarded to your laptops. Watney, your pile of fanmail is getting so large I had to add extra storage to your profile for it."

"Sweet," Watney said, rubbing his hands together as he pulled up the first of several letters. "I wonder who we've got today? Oh look at that, there's one from Robert Downey Jr.!"

"Who? Oh, isn't he that old guy?" Johanssen asked, and ignored Watney as he sputtered. "Hey, Vogel, you've got a telemetry update, and Commander, there's a space weather advisory for the crew."

"What does it say?" Lewis asked, coming to stand behind Johanssen.

Johanssen scrolled. "Hmm... we're going to be passing through the tail end of a comet debris field starting this afternoon, so there will be a slightly increased chance of micrometeoroid impacts." The Hermes had been built with several layers of shielding in place to withstand small debris impacts, but there was still a concern that something large enough or lucky enough could punch a hole in something sensitive.

"Do we have any ability to maneuver around it?" Lewis asked.

"The telemetry update has the minor course adjustment," Vogel said. "It will take us away from what NASA says is the area with the highest concentration of debris. We will also orient Hermes to present the lowest surface profile to the debris, and close the shutters over the windows."

Johanssen added, "But we're low on fuel, and there's only so far we can go. And most of the debris is too small to track."

Lewis nodded; that was what she had expected to hear. "Nothing much we can do about it unless we get hit by something, then," she said. "Pass along the word so Martinez and Beck know to keep an eye out for any evidence of damage, and everyone, refresh your memory about decompression procedures-- and where we keep the patch kits. How long until we're past this?"

"We should be through the worst of it by this evening around 7."

"Good to know. I'm sure we'll be fine."

"Yes, ma'am."

 

***

_The trail of debris left behind after Comet Siding Springs's close encounter with Mars was made up of minuscule pieces of rock, dust and ice. These tiny pieces-- anywhere from a micrometer up to centimeter in diameter-- continued in their path for the next twenty years, gradually spreading out as time went on, but losing little of their velocity. Most of them would continue on their lonely journey for millions of more years to come._

_The Hermes passed through the main body of the debris field without incident; although it hit multiple leftover pieces of the comet, the outer layer of the Whipple shield worked as designed, breaking them up on impact and spreading out the force of the resulting pieces across the second and third layers without breaching the hull._

 

***

The ferns have been measured. It'll be a while before I can really tell for certain, but so far my preliminary results are showing the same weird (yes, that's a technical term) growth rates as Beck's. Maybe it wasn't user error after all. I'll have to apologize to him.

...Nah.

We're past the worst of the debris field, so I can relax about that. Or try, anyways. Dr. Shields claims I have 'hypervigilance caused by post-traumatic stress' or something to that effect. I say it's a perfectly natural reaction to having spent over a year and a half in an environment where literally everything could kill me in a hundred different ways.

Heck, I'm _still_ in that kind of environment. Space is an asshole.

Anyways... everybody else is still busy with their work (sigh), but my evening is free. I watched everything I brought already on the trip to Mars, so I've been raiding the others' media storage in a bid to fend off boredom.

All Lewis has is more '70s TV, which, _hell_ no. Vogel's shit is in German. Beck has a hundred thousand medical journals, as well as all 8 seasons of _House_. Johanssen has the entire run of _Doctor Who_ , even the weird mid-2020s stuff. And Martinez brought all 10 of _The Fast & The Furious_ movies as well as the spinoff _Hobbs and Shaw_ ; pure mindless entertainment at its finest.

 _The Fast and the Furious_ it is.

 

***

 

_A comet's debris field doesn't have strictly defined edges. Although the Hermes' adjusted course had taken her away from the main concentrated area of ejected material, a number of stragglers lurked nearby._

_One of these was a piece of rock and ice the size of a marble which crossed the Hermes' path, moving at a relative velocity of 56 km/s._

 

***

Okay, seriously, fuck space! I'm so sick and tired of this shit!

I was a grand total of 30 minutes into watching the movie when the decompression alarm went off. As you can imagine, I nearly shat myself. I was back on the Hermes! That sort of shit wasn't supposed to happen anymore!

After a half second of sheer panic, I realized I wasn't dead, I was still able to breathe, and my ears hadn't popped, so it couldn't be that bad. At least, as _not bad_ as any kind of loss of atmosphere can be on a tin can flying in outer space.

Ugh. I _hate_ space debris.

Way back in the day on the old International Space Station, the procedure for a loss of atmosphere event was to rush to the Soyuz descent modules and prepare to jet back to safety on Earth. Those assholes had it easy. The Hermes is 100 million kilometers too far away from Earth for the luxury of abandoning ship; we either fix the problem or we die.

First things first. Each section of the Hermes is designed to seal off from the rest in case of exactly this kind of situation. I leapt-- well, as much as I could; the gravity in the Rec is only 0.2g, so it was more like a very long _bounce_ \-- for the hatch, ignoring the way it made my ribs complain. As I pulled out the emergency seal, Johanssen's voice came over the ship intercom.

"Hermes, be advised systems are reporting a hull leak in--"

The alarm shut off.

"--Semicone-B," she finished.

I kept fitting the seal into place, because there was no reason to risk it, but I held off on turning the crank.

"Everyone, sound off," Lewis said.

"On the bridge," Martinez said immediately. "A-ok here."

"In the bio-lab," Beck responded. "All good."

"Also in the bio-lab," Johanssen said. "No problems."

"I am in the crew quarters," Vogel responded. "All is good."

"In the Rec," I said. "Nothing wrong that I can see."

"And I'm in the reactor room; no problems here. Johanssen, report," Lewis said.

"I'm checking," she said. "Okay, the computer is showing a momentary dip in pressure in Semicone-B from 1.0 atmospheres to 0.91, which lasted for twenty-eight seconds. Then the leak must have gotten plugged somehow, because atmo is holding steady at 1.0 again after backfilling from the reserve tanks. Current air reserve time, including what we get from electrolysis, is... 5,562 hours. Plenty for the trip back."

"And how long would our reserve time have been if the leak _hadn't_ stopped?" Lewis asked.

"With everything factored in..." Johanssen paused. Her voice was tight when she came back on. "644 hours." Not quite 26 days.

We still have 150 days left on our trip home, so you can see how this was a fucking problem.

Beck came on. "That's a pretty big leak," he said. "Did we get spiked by a micrometeoroid? I thought we were past the worst of it."

"Past the worst of it, yes, but not past _all_ of it," Vogel said.

"More importantly," Lewis asked, "where is the leak? Was the UBND able to pinpoint the specific hull panel, Johanssen?" The Ultrasonic Background Noise Detector used sensors set all over the hull to listen for the high-pitched noise of air escaping the Hermes and then triangulated the location based on that data.

"No, the incident didn't last long enough," she said. "Sorry."

"Guess we have to do it the old fashioned way then. Beck, Vogel, Martinez, head to Semicone-B and conduct a visual inspection. See if you can identify the problem. Make sure to leave a clear path back to the rest of the station so you can evacuate if necessary. And take the handheld detectors as well, just in case it starts up again."

"Great," Martinez grumbled. "We get to go stare at the walls."

"You sure do. Johanssen..."

"I can try going through the raw data and see if the UBND had made some kind of preliminary location estimate before the incident ended."

"Good. And Watney, check the exterior cameras. See if you can identify the source of the leak that way. Make sure we're not losing pieces off the ship. I'll go let NASA know what's going on, and join you when I'm done."

"Aww man, you're putting me on camera duty?" I said.

"No arguments. Your ribs are still healing, I don't want you doing anything strenuous."

Ugh. My freaking ribs again! On Earth they'd have been healed already! Checking for leaks wasn't exactly hard work, and it would go faster with more people.

"Doctor's orders," Beck put in. He probably knew exactly what I was thinking, the bastard.

" _Commander's_ orders." Lewis's voice was firm.

I grimaced, but in the end I didn't argue-- Lewis was in charge here. Besides, there was one plus side to camera duty. "Tell me I at least get to use the robot arm?" 

Lewis's sigh was audible over the intercom. "Yes, you get to use the robot arm."

Sweet!

 

***

 

The Hermes' robot arm-- or, in official terminology, _Canadarm 4_ (yes, it's a  _Canadian_ robot arm, and no, it doesn't run on maple syrup)-- is situated on a running track along the spine of the Hermes. Ten meters long, it can slide along to reach most parts of the ship, and you can swap out the payloads for different purposes.

Before you ask: it wasn't designed to stand up to lots of torque, and trying to use it to grab me out of space would have just ended up with a broken robot arm.

In this case, the payload we were using was the RELL-- Robotic External Leak Indicator. It's basically a space-hardened mass spectrometer that can detect the tiniest amounts of gasses present in a vacuum. Pretty useful for finding leaks!

I slid into my chair on the bridge, pulling up my workstation and the arm controller. I put my ear mic in, so I could listen to the others. The RELL was already in place on the robot arm from the last time we'd used it, so it only took a few minutes to have it up and running. I set it to travel down the Hermes towards Semicone-B, which was one of the modules on the Hermes' spinning ring. It moved pretty slow, to avoid accidentally bumping into anything. While I waited for it to get there, I pulled up Exterior Camera 3, which was the closest camera on the Hermes itself. It showed the rotating section of the ship against a backdrop of stars. Mars wasn't visible from this angle, but if it was it would have been a round dot in the distance, the size of a dime. Earth was a small bright star in the distance.

Zooming in on Semicone-B, I started examining the structure for any signs of damage or failure.

The problem with having been in space so long quickly became apparent. Debris was rare in deep space, but not non-existent, and the skin of Hermes was pockmarked with old damage. I spotted a couple places where holes had been repaired already-- Beck and Vogel on EVA, I presumed-- but a lot of them had been determined not to be a danger and had been left as is. That made it complicated as hell to figure out which ones might be new.

After a few minutes, motion in the corner of the camera indicated our friendly Canadian robot arm had arrived. I swapped over to that view, which allowed me to get in closer to the section in question. The shutters had been lowered again to check for leaks in the windows, and like this, I could see Martinez, Beck and Vogel. Martinez had his face up against the glass, peering at the window seal. I couldn't resist the opportunity; I snapped a picture. _Perfect._

"Anything so far?" Lewis asked, coming up behind me. She snorted when she saw the image on my screen.

I coughed and quickly minimized it in favor of the live camera feed. "Uh, no immediately obvious problems. Structure is in good shape. I can't see any crystallization that might indicate a liquid leak. I haven't made it around to the other side yet, though."

"I'll pull up Exterior Camera 2," Lewis said, sliding into her chair and picking up her own mic.

"Did NASA have anything to say?" The round trip comm lag from NASA had dwindled as we got closer, and was now down to about eight minutes.

"Check for leaks," Lewis said dryly, as she scanned the outside of the ship. "Keep them updated. If the problem reoccurs, and we can't fix it quickly enough, seal Semicone-B off from the rest of the Hermes and let it go full vacuo."

I grimaced. "That cuts off a pretty significant portion of our living space," I said. There were still 150 days left before we arrived back at Earth, and a guy needs his alone time, y'know? _Ahem_. That's one of the nice things about not being starving anymore, I gotta admit. Things are working much more reliably.

"Yeah, but we're already down to two-thirds of our reserve oxygen after the stunt with the VAL, and they're not comfortable with us losing any more--"

The decompression warning alarm went off again.

"Shit!" I said, and bolted up from my chair. My ribs screamed at me, and I sank back into the chair, trying not to gasp. Fucking ribs! Maybe Lewis had a point. Ugh, but I also hate not being there to help.

On camera, Martinez and the others were still searching methodically, though their movements had taken on new urgency. Lewis flicked on her comm. "Johanssen."

"On it. Just give me a sec. The system's still searching."

"Martinez?" Lewis asked.

"Nothing obvious!" he said.

"It's a big fucking leak, we should be able to hear it!" Beck said.

"So shut up, then!"

I scanned the outside of the ship, switching from camera to camera, looking for anything that might indicate a leak. Air was invisible, but everything else in the air wasn't necessarily-- there should at least be small water crystals as the humidity froze on contact with vacuum.

Nothing. Fuck. I moved the RELL to examine another potential hole. Nothing. 

There was a long pause as we waited for the system to finish working. I could see Vogel running his detector along the wall. Beside me, Lewis scanned the external cameras as well. 90 seconds passed. It didn't seem like the leak was going to stop on its own this time.

"Last time I was trying to find a leak I burned my own hair and used the smoke to locate it," I said offhandedly, moving the RELL along another few inches.

Lewis gave me a weird look.

"What? I'm just saying, something similar could work here."

"We're not setting anything on fire again, Mark," Lewis said flatly.

"Says the woman who set off a bomb on her own ship. I didn't say we had to use smoke, but maybe some other particulate--"

"Got it!" Johanssen interrupted triumphantly. "It's in Hull Panel 19. Towards your left, Vogel."

I sent Canadarm that way with the sniffer and pulled up the ship schematics on the other screen. That hull panel was along the short side of the module, where it was more difficult to see with cameras. It was where the connecting rails that linked Semicones A through D into a circle attached. The rails are also used to house the highly-toxic ammonia cooling loop that keeps the power systems in the ship from overheating and frying us all.

RELL had its own medium-res camera, mostly to make sure no one bumped it into anything accidentally, and I switched to that as Canadarm got close enough. From the outside Hull Panel 19 was a flat piece of aluminum; underneath were several more layers of the Whipple shield. Because of the angle of the module it wasn't as exposed to debris impacts, and the surface was relatively pristine. I sent RELL towards the first impact scar I saw.

Lewis leaned over to watch as I moved the camera closer. RELL wasn't detecting anything, but it only had a range of about a meter. I left it there while it worked. The decompression alarm wailed away in the background; it made my teeth clench.

"Johanssen, is this leak losing air at the same rate as before?" I asked. 

"Yeah, approximately," she came back.

Johanssen had said we had 664 hours until the air ran out, but we would be in trouble even before that; we needed at least 3600 hours worth left over for the trip home. That didn't leave much of a margin for error.

"We've got 9 and a half days before we're shit out of luck," I said to Lewis. "When Hermes had a leak during Ares I, it took them three weeks to locate it."

"That was a leak in the window seal, not a micrometeoroid impact," Lewis said. "And their UBND was malfunctioning."

She was right. Nine days was plenty of time, I told myself. Even if we couldn't find the leak itself, we could always just seal off the affected area and fix it at our leisure. We weren't going to run out of air. I wouldn't be doing any good by going down there to help find the leak.

The RELL results came back. Nothing.

"I'm just saying, some kind of particulate would find it in no time. Maybe we can rig up something with the water system, get a fine mist in the air--"

"Mark." Lewis's hand settled on my shoulder. "At least give the equipment we have a chance to do its job before you start jury rigging things, alright?" 

"...Right." I took a deep breath, and sent the RELL along to another potential hole.

That one came up negative, too.

"I don't see any other suspicious areas," I said. "You know, maybe we're looking for the wrong thing. Maybe it's a faulty window seal again, and the timing is a coincidence. Or it could be a software error, or..." My eyes caught on something as the module continued to spin, and I stopped, squinting at the screen. "Huh."

Lewis leaned over. "What do you have?"

I pointed at the screen. "That dark spot, just under the coolant line. Does that seem irregular to you?" The Hemes has lights on the outside of the ship, but the coolant line in question was in shadow. "Because it sure looks irregular to me."

Lewis sat forward. "It could just be the seal... hmm. No, you're right." She glanced at the schematics. "The seal wouldn't cast a shadow like that. And I'm not showing any repairs or changes in the logs that might be the cause."

"That's what I thought." I sent RELL closer to check it out.

"Any sign of intrusion on the inside?" Lewis asked.

"Nothing we can see," Beck radioed back.

RELL's sensor beeped as I brought it closer to the leak. "Oh, _hello_ there. I'm showing nitrogen, oxygen, and some good ol' H20," I said. Much like that HAB, the composition of air on the Hermes is a 75-25 mixture of nitrogen and oxygen, with a humidity of about 60%. I frowned. "And... hmm. A small amount of ammonia."

"Coolant leak?" Lewis asked.

"Maybe.Not a very big one, though." The coolant and the air weren't supposed to mix, for obvious reasons. If it was a leak, the space rock had managed to punch a hole in both systems. Even my luck wasn't that bad, right?

Ahahaha. Yeah, right.

Beck said, "Humans produce ammonia when they breathe, so there's a small amount of ammonia in ship's air normally. It could just be from that."

I grimaced at the screen. RELL had been designed to say whether or not a gas was present, not to be precise about _how_ _much_ \-- it gave its results in a graph of intensity over atomic mass unit. I could tell there was significantly less ammonia than oxygen or nitrogen, but that was about it. "Hard to tell. Any of you guys know how to read data off a mass spectrometer?"

"I do," Vogel said.

"Great! So, there's a couple large squiggly lines at 28 and 32, and a smaller one at--"

"You can look at it later," Lewis interrupted. "Right now we need to get the air leak found and sealed. Martinez, Beck, Vogel, if you smell any ammonia, I want you to get out of there immediately, it's incredibly toxic."

"Copy that, Commander," Martinez said, and there were murmurs of agreement from the others.

"It shouldn't be able to backdraft into the cabin," I said. "The vacuum will be sucking everything straight out of the ship."

Lewis nodded, but said, "Better safe than sorry," which might as well be NASA's motto. (For the record, NASA's real motto is _For the Benefit of All_. Kind of sappy if you ask me.) "Martinez, the hole we're seeing is about a meter from the outer corner," she said. "It should be just below the storage rack on that side. Anything?"

"Not a damn thing, Commander," Martinez said.

Lewis frowned. "Johanssen, how much time do we have left before our oxygen drops below necessary reserves?"

"226 hours," Johanssen answered.

Lewis frowned, thinking. "Okay. Johanssen, go to Semicone-B and help Martinez look for this leak." Johanssen acknowledged the order, and Lewis continued, "Beck, you and Vogel go prep for an EVA. If we can't find this leak on the inside, you're going to have to patch it from the outside."

"Copy that," Beck said, and Vogel said, "Yes, Commander."

I swiveled in my chair to stare at Lewis. "And I will be...?"

Lewis pointed at my chair. "Seated right there, keeping an eye on the ammonia reading."

I took off my radio headset and set it on the console. " _Commander_. Seriously?"

Lewis turned to face me and took off her headset as well. "Yes, Mark. Seriously."

"At _least_ let me help Johanssen and Martinez check for the interior leak."

"You've got the ship schematics; look at those and see if you have any ideas where it might be coming from."

Frustration bubbled up in my chest. I bit it back down, trying to avoid saying something I would regret. "Is the entire rest of the mission going to be like this?" I asked, spreading my hands. "Lewis, you _know_ me. If you try and wrap me in bubble wrap, I'm going to go crazy." I thought about it, then edited, "Even crazier."

Lewis leaned forward, elbows on her knees. Her eyes were very intense. "Mark, I know you don't like hearing this, but _you are still recovering_. Beck gives me regular reports." She ticked her points off on her fingers. "Your weight is still way too low. You can barely run a mile on the treadmill in 0.4g; you have the effective stamina of an eighty-year old. And don't think I didn't notice your ribs giving you trouble earlier."

I grimaced, hand going to my side.

Lewis continued, "What happens if something goes seriously wrong? The others would be paying more attention to keeping you safe than they are to themselves, and that's how injuries happen. Don't get me wrong, we could stand to have you in there helping right now, but I can't afford to have another member of the crew out of commission."

I turned back to the console, swallowing. After a moment I said, "Fair enough."

Lewis watched me for another few seconds. Then, seemingly satisfied, she turned back to her console and picked up her radio. "Beck, Vogel, how's that EVA prep going?"

 

***

 

I bet you're expecting me to tell you I waited until Lewis left the bridge and then snuck out to check on the leak myself.

Yeah, not so much. I may chafe at authority, but Lewis is the mission commander, and what she says on board ship goes.

Besides, she had a good point. I hated to admit it, but I wasn't in great shape.

Instead, I pulled up the ship schematics again and began going over them with a fine toothed comb. Something was bothering me about the results we were getting off the RELL. The level of ammonia was slowly dropping, but it hadn't gone away. That smelled like an ammonia leak to me, but the odds that a meteorite had managed to punch a hole in both systems were... well, even taking my luck into account, they were pretty low.

And where the hell was the hole on the inside of the cabin that was letting all the air out? Someone ought to have found it by now, right?

The spacesuits used for EVAs these days are significantly lighter and easier to put on than the ones they had during the Apollo missions. Soon enough, Beck radioed, "We are suited up and ready to go."

"Good. You have the patch material?" Lewis asked.

"Yes ma'am," Beck said.

"Alright. Go take a look. Seal it up if you can."

I pulled up the overview that showed the coolant system. The thing was complicated as hell.

You would think being in space our problem would be keeping the ship warm enough, not cool. Space is really fucking cold, right? Except our reactor plant and all the electronics put out a _lot_ of heat, and unlike Earth-- or Mars-- space is cold because it's mostly vacuum. There's three methods of getting rid of heat: convection, conduction, and radiation. Convection and conduction both only work when you've got enough molecules around to bump uglies with each other, and there's not a lot of those in vacuum. That leaves radiation as the one way of getting rid of all the excess heat.

Hermes' cooling system, much like the internet, is made up of a series of tubes. The inner set uses pure water because it's closest to the habitable areas, and as I've mentioned, ammonia is really fucking bad for humans. The outer set uses high pressure liquid ammonia. (Why even use something that toxic? Well, ammonia is a vastly better refrigerant.) 

The water absorbs heat from the Hermes, which it then cycles through the system until it reaches one of several connection points to the outer set of tubes, where it exchanges the heat. These points are called-- inventively-- interface heat exchangers, or IFHX. Once the heat has been transferred into the ammonia lines, the ammonia transports it down the Hermes to the cooling vanes on the back end of the ship, where they emit the heat as radiation. And then the whole process starts over again.

The rails linking the Semicones contain ammonia coolant lines, because the rails were necessary for stability and NASA figured why waste the space? They radiate out a minimal amount of heat-- the cooling vanes are vastly more efficient-- but it all helps. There was an interface heat exchanger on both ends of the railing, I saw from the schematics.

Okay, let's work through the steps. If the meteorite had gone through the hull of the ship itself, we'd have found it by now. So something weirder was going on. What would happen if the meteorite had knocked a hole in the coolant line itself?

"Exiting the airlock," Vogel radioed.

First, there would have been a rush of ammonia escaping. The ammonia is kept at 390 psi. A drop in pressure means a drop in temperature, too, and the ammonia is already pretty cold. Ammonia freezes at -78° C; exposed to the vacuum of space, it would have reached that point pretty quickly.

On the other side of the IFHX is the water coolant system. Although heat passes between the two, the two coolants don't physically intermix at all under normal circumstances. As the temperature of the ammonia dropped, the water temperature would start dropping, too. There's safeguards in place to keep the water from freezing, but they weren't designed to deal with such a significant temperature differential. As the ammonia froze, they would have struggled to keep up and eventually failed, and the water would have frozen as well. Which would have caused... what?

I rubbed my face. "Hey Johanssen, where did you store the cooling system manuals?" I asked.

"They're under System > Resources," she radioed back. "Why? Got something?"

"I'm not sure yet. Tracking down an idea." If the coolant had frozen, the Hermes should have notified us. "Have there been any other alerts beside the decompression alarm?"

"Just a sec, I need to log in." There was a pause on her end. I navigated through the system directories and pulled up the cooling system manual, flipping through pages until I got to the section on the IFHX.

"So, this is weird," Johanssen came back after a minute. "The water cooling system is saying that it initiated emergency shut down and isolation procedures for Section 2.b after a sudden drop in pressure. But that doesn't make sense, that section isn't anywhere near Hull Panel 19."

The IFHX is made of a lot of really thin layers of plastic that are not designed to be frozen. Frozen material becomes brittle and breaks.

"It does if the ammonia cooling system is what got hit," I said. "The drop in temperature could have breached the IFHX and then hey presto, it all gets sucked out into space."

Martinez said, slightly out of breath, "That still doesn't explain why we have an _air_ leak."

"I know, I know. Still working on that part." I flipped pages in the manual. Was there any place where the water coolant system met air? There had to be something.

Three paragraphs down page 128 was a diagram labeled _Expanded View: Gas Trap_. The gas trap filters non-condensed gasses out of the water coolant line to keep everything running smoothly. And to do that, it... vents them into the cabin. "A- _hah_!"

"Got something, Watney?" Lewis asked.

"I _think_ so-- anybody know what the psi rating on the coolant gas trap is?" If it was too low, it might have blown after being exposed to vacuum.

"Beck to Hermes. We're approaching the location of the breach. It looks like a pretty big hole; this has to be it. I'm about to break out the patch kit."

"Beck, Vogel-- before you do that, do you see any frozen ammonia around the hole?" I asked urgently.

There was a long pause. "Yes, there is a small amount," Vogel radioed back.

So, if I was right, there was a hole straight from vacuum, through the ammonia coolant line, into the water coolant line, and straight into the cabin. If they patched the hole, it would stop the air leaking... but the ammonia coolant line would still be connected directly to the air we were breathing. And once the pressure was stabilized, the system would try to backfill what it had lost with stored ammonia. 

"Ah, _shit_. Beck, Vogel, wait!"

 

***

 

[Mission Day 749]

Well, it's been a fun two days. 

After pulling Beck and Vogel back from their EVA-- and let me tell you, they were pissed about that-- we worked with NASA to figure out how to fix the leak without filling the ship with ammonia and killing everyone.

Spoiler alert: Johanssen went in and modified the coolant system's programming so it wouldn't backfill automatically. Then Beck and Vogel went back out to patch the hole in the side of the ship. Sure enough, that stopped the air leak! And there was minimal detectable intrusion of ammonia into the cabin.

We ended up losing 103 hours of air, but that still leaves us with 5,467-- plenty enough for the trip home. As long as nothing else goes wrong. 

Fixing the coolant system in that section is going to be a major hassle. We're going to have to swap out the gas trap and the IFHX-- both of which are going to require significant EVA time-- and then run diagnostics on everything before we can get that section up and running again. In the meantime that section of the ship is going to be miserably warm, but it's better than dying! 

We've been working so hard the last two days that NASA actually gave us a down day today-- cleared our schedules of everything except the most pressing items. All I've got is maintenance checks, and those aren't until later in the day.

So... back to watching the movie it is.

 

***

 

"Hey, Mark," Martinez said, wandering into the Rec with a pack of M&Ms. He tossed a few into his mouth. "Ooh. Is that _The Fast and the Furious_? I love that movie."

"I know; I stole it from your collection," Watney said.

"Thief!" Martinez declared, then asked, "Mind if I join you?"

"I require tribute," Watney said, hand extended. Martinez looked down at the M&Ms and then handed them over with a heavy sigh. He settled onto the couch next to Watney, kicking his feet up on the coffee table. Watney crunched away happily at the chocolate.

Beck came in a few minutes later. "Having a movie night?" he asked.

Watney made a production of checking his non-existent watch. "I'm pretty sure it's movie _morning_ ," he said.

"We're in space. It's night all the time," Beck said.

"Oh, whatever. Just sit down and join us."

"Hey, he doesn't have to pay tribute?" Martinez asked.

"Witty repartee _is_ his tribute," Watney said. "God knows I don't get it from you."

"Ouch, man!" Martinez grabbed Watney around the shoulders-- very gently-- and attempted to ruffle his hair. Watney retaliated by trying to smash an M&M on his face.

Beck watched this all with a long-suffering expression. "I feel like as your doctor I should be putting a stop to this," he said.

"You said-- I was supposed to be-- getting exercise, right?" Watney asked, ducking Martinez's arm. He winced, a hand going to his ribs. 

"Yeah, but not this kind of exercise..."

In this middle of all this, Johanssen came in holding a book. She ignored the kerfuffle and settled in on Watney's other side without asking.

Vogel was next. He came carrying a large plastic bag. Watney's eyes widened, and he pulled away from Martinez. "Is that popcorn?" he asked, reverently. "Where the hell did you get that?"

Vogel tapped the side of his nose. "German secret," he said.

"Wait, what? That doesn't even make any _sense_ \--"

"He got it from me," Lewis said. Her hands were full with drink packs. "I had some stashed away. No beer on this ship unfortunately, but I did grab hot chocolate. And coffee."

"Hey, now the real party's starting," Watney declared. Lewis passed him a coffee without asking, and he stuck a straw in the bag. "God, I missed this stuff," he declared to the room at large.

"You missed shitty space coffee?" asked Johanssen, the other coffee connoisseur on board. "That's pretty sad."

"Try living for six months off caffeine pills dissolved in hot water, and trust me, you'll learn to appreciate shitty space coffee," Watney said.

"Scoot," Lewis ordered, and Johanssen made room for her, squishing Watney in betweenher and Martinez. He didn't seem to mind. "Mind rewinding the movie?" Lewis asked. "I haven't seen it."

Watney shook his head in mock-despair. "Serious question: have you ever seen anything that _wasn't_ made in the 70s?"

Lewis thought for a moment, hand on her chin. "Well, I'm about to see this movie," she said. Watney groaned.

Martinez grabbed the remote and rewound the video to the starting point. "Okay, we _clearly_ have some work to do," he said.

Lewis leaned over Johanssen to hand Watney the popcorn first. "Good work these last couple days," she said quietly, as the opening sequence began to play.

Watney shrugged, grabbing a handful. "Hey, I don't want to die this close to home either," he said, then waved grandly at the screen. "Now pay attention! We'll teach you to love other things besides disco and big hair soon enough."

"I'm looking forward to it," Lewis said, and settled back on the couch.

**Author's Note:**

> I tried my best to keep the science in this accurate; however, I am definitely not an expert in astronomy/astrophysics/orbital dynamics/aerospace engineering, so there may be unintentional errors. I based a lot of the details of the Hermes on equivalent systems on the ISS (thanks for posting all your research online, NASA!) In a few cases I took liberty with some of the facts for dramatic effect (especially re: Comet Siding Springs). 
> 
> The descriptions of the Hermes in the book don't always match up with what it looked like in the movie. I've tried my best to merge the two, but it was occasionally tricky.


End file.
